Until recently, fabrics used to form apparel have been either knitted or woven, the various fabrics comprising yarns formed of natural or synthetic fibers or filaments, or combinations thereof. As the materials and textile arts have progressed, improved fiber, yarn, and fabric constructions have been developed in response to the demand for certain performance characteristics in the ultimate article of apparel. These characteristics include hand, stretch, hydrophobicity or hydrophilicity, pill-resistance, stain resistance, colorfastness/washfastness, etc. Accordingly, various dyeing and finishing formulations and processes have been developed for use with knitted and woven fabrics. In particular, various dye formulations and dyeing processes have been developed with a goal of dye/color uniformity, and dye colorfastness after multiple home launderings, when measured according to established industry standards.
Nonwoven fabrics, on the other hand, have conventionally been used to form expendable articles such as linings, disposable sheets and wipes, diapers, disposable napkins, etc., but not apparel. While certain dyeing processes have been developed for nonwoven fabrics, dye uniformity and colorfastness heretofore have not been important performance characteristics of nonwoven fabric, and thus dyeing and colorfastness standards do not exist for nonwoven fabrics. Although it would seem that existing dyes and dye processing could be readily used on nonwoven fabrics, nonwovens present a unique set of challenges.
First, nonwoven fabric constructions typically comprise multiple webs or mats that are interconnected together to form a fabric. Hydroentanglement or air entanglement are two mechanical processes for entangling the fibers in one web with the fibers in another web. Also, the multiple webs may be stitched together. In any event, however, since nonwoven fabrics are generally formed from yarns of smaller (denier) fibers, and since multiple webs or mats are involved, these fabrics have substantially greater surface areas that must be dyed. Further, when more than one type of fiber/yarn is used to form the nonwoven fabric, dyeing is complicated when the different fibers/yarns have different affinities for different dyestuffs. Thus, multiple dyeing steps comprising a different dye bath for each fiber or yarn type has been required.